Science time! That crater our friends are walking past is a simple crater. Simple craters are shaped (roughly) like bowls.

Complex craters, on the other hand, are larger, shallower, and often have a central peak or uplift. This is because the ground has rebounded after the cratering event. Complex craters are generally created by larger objects than create simple craters.

Larger than the complex craters are impact basins, which are hundreds of kilometers across and seriously deform the crust. The largest impact basins form some of the Moon's maria (seas).

Simple and complex craters form on the surface of the other moons and planets as well. Meteor Crater in the American southwest is simple, whereas the western Clearwater Lake in Canada is complex. The ring island in the lake is the central uplift. Some complex craters, such as this one, have ring structures instead of central peaks.